Historically, mobile consumer devices such as media players, smart phones, tablets and the like have relied on connections to other devices, such as laptop or desktop personal computers (PCs) to acquire content, exchange data, and charge the device's internal battery. For many years now, that has been accomplished through USB ports on each device. The use of USB technology is suitable for such needs since it is commonly available, familiar to the end user, cost effective and ubiquitous. USB protocols require a point-to-point connection in which one end is the USB host or master, and the other end is a USB device or slave. In this way, the flow of messages between the two devices is managed and controlled, whereby the USB device responds to messages initiated by the USB host. Historically, PCs have provided USB host ports for connection to simpler USB devices such as printers, memory sticks, mobile phones, etc. The USB host has a greater burden of software and hardware requirements than a USB device, so it has made sense to designate the PC as the USB host in such systems.
In vehicle systems that employ USB connections, the same concepts apply. In such systems, the vehicle is typically the USB host. The USB host function is often embedded into a component of the vehicle infotainment system, such as into the radio or other control module. Typically, multiple USB ports are strategically designed into the vehicle in locations convenient for the driver and passengers to connect their consumer devices. Once a consumer device is connected to one of the ports, the device begins charging and the vehicle infotainment system can access content on the consumer device. This is useful to enable features such as streaming music, video and other services the device may provide.
Such a system requires that each of the USB ports be physically connected to the vehicle's USB host in a manner suitable for USB data flow. This is accomplished through electrical cabling which is embedded in the vehicle, and which connects each of the ports to the USB host. Since there can be many USB ports in a vehicle, and each port requires a cable to connect the port to the USB host, it is desirable to share cabling when possible to minimize cost and mass of the vehicle. This is accomplished through the use of USB hubs. USB hubs allow a single USB host to connect to multiple USB devices over a single cable between the USB host and the USB hub. As shown in FIGS. 1 and 2, a single USB hub can connect one USB host to several USB devices. Specifically, FIG. 1 illustrates a system wherein a self-powered USB hub module 110 having a plurality of USB ports 112 connects to a plurality of USB devices via a plurality of consumer-facing USB ports 114, while FIG. 2 illustrates a system wherein a self-powered USB hub module 210 provides not only a plurality of USB ports 212 which are in communication with a plurality of consumer-facing USB ports 214, but also a Secure Digital (SD) card reader 216 which is connected to a consumer-facing SD card connector 218. Other portions of FIGS. 1 and 2, such as Power Management 116, 220, are standard in the industry and self-explanatory upon viewing FIGS. 1 and 2.
Furthermore, as shown in FIG. 3, multiple USB hubs can be tiered, such that USB hubs connect to other USB hubs. Specifically, FIG. 3 illustrates a vehicle system architecture that includes a central vehicle microcontroller 310 (also referred to as the head unit 310). Connected to the head unit 310 are components or systems such as displays 312, the audio or entertainment system 314, and the driver controls 316. The head unit 310 may be architected as a single module encompassing all functions or distributed such that various functions are managed by individual modules. The head unit 310 includes a Root USB hub 318 which is typically connected to one or more downstream USB hubs 320 A-D distributed throughout the vehicle. Each USB hub 320 has a plurality of downstream ports 322 (at least one of which may be an SD reader 324 or USB audio device—not shown), thereby effectively providing that each USB port 320 A-D in the vehicle has a connection to the USB host 318 or head unit 310. In FIG. 3, for example, the Root Hub is embedded in the radio, and is connected to four (4) self-powered USB hubs 320 A-D, wherein one is in the vehicle's center console 320A, one is in the vehicle's center stack 320B, and two are in the vehicle's rear seats 320C, 320D.
Recently, mobile devices such as smart phones have gained in popularity. This is, in part, due to their usefulness as standalone computing devices. With advances in consumer electronic technology and increases in the speed of mobile networks, these devices are no longer reliant on being connected to PCs to access content. These smart mobile devices now have many of the same hardware resources, connectivity and software operating systems that only PCs had in past years. As has been the case with desktop PCs, accessories for these mobile devices have become available to aid in their ease of use. These accessories have included devices such as keyboards, mice, displays, touchscreen, audio systems, and other interface devices. These accessories commonly connect via a USB connection. By way of established convention in the consumer electronics market, these accessories are typically low cost and limited in USB capability to act only as a USB device. To connect them to a smart phone, the smart phone must be the USB host. Therefore, leading mobile device manufacturers and system designers have begun designing their mobile device products (i.e. smart phones, tablets, etc.) to support both USB host and USB device roles. In other words, the phone may configure itself such that it can function as a USB device when it needs to be, or as a USB host when it needs to be. Recently, the system level design thinking has shifted towards viewing smart phones as the USB host, and any device connecting thereto as the USB device. Again, this is not surprising since this is exactly how laptops and PCs work today. Extending this trend into the future, it can be predicted that the smart phone will act primarily as the USB host, and will rarely or never act as a USB device. This presents some problems for automotive systems.
As explained previously, automotive systems have a USB host and require USB devices to connect to it. If a phone acts as a USB host, then the system will not function since by USB convention, two USB hosts cannot directly connect with each other. Automotive manufacturers desire compatibility with smart phones and are therefore motivated to adapt to this changing technology. A redesign of the USB architecture in the vehicle is thus necessary such that the vehicle can act either as the USB host (when necessary to connect to USB devices such as memory sticks, thumb drives, etc.) or USB device (when necessary to connect to USB hosts, such as a smart phone which demands to be USB host rather than USB device.
The USB organization has added a standard that addresses the need for devices to act as either USB host or USB device and as such can be considered a “dual role” USB controller. It is referred to in USB nomenclature as “On The Go” or “OTG” for short. Any device that meets the OTG standard can act as either USB host or USB device and can change roles dynamically. Therefore, one possible approach to modifying the vehicle USB architecture to support all use cases is to upgrade the vehicle's USB host to USB OTG. This solution addresses the issue but has some disadvantages. First, USB hubs do not support OTG and can no longer be used in the system. Each consumer accessible USB port that supports OTG must have a dedicated wire link to a dedicated OTG controller in the head unit thus negating the wiring savings associated with use of USB hubs. As a result several costly cables may need to be added to the vehicle's electrical system. Second, there may not be enough OTG controllers available in the head unit to connect to each of the vehicle's user accessible USB ports. This then forces the vehicle designer to choose a limited number of the many USB ports in the vehicle to support the OTG function and run dedicated USB cables to them. This can lead to user confusion and dissatisfaction since only certain consumer ports support the required functionality. Also, ports that support OTG may be co-located with other physically identical ports that do not. If the user chooses the wrong one, the applications they desire to run from the consumer device that requires USB host mode won't work.
Another possible solution is to implement custom USB hubs wherein the USB hub is able to dynamically swap its upstream port with one it's downstream ports when commanded to do so. System solutions built with this concept still require OTG controllers in the head unit but benefit from the fact that no additional wires need to be installed in the car. The existing USB cable between the USB OTG host and the USB hub can facilitate the necessary USB communications between the USB OTG controller in the head unit and a consumer device in USB host (such as a smart phone). This solution also has some disadvantages however. For example, when the USB hub is commanded to swap it's upstream port with a downstream port, all other downstream ports of the USB hubs lose their data connection with the head unit. While in this mode the head unit access to the other downstream ports of the USB hub cease. This may prevent use of certain vehicle system functions such as navigation or audio playback that may need consistent access to the other downstream ports of the hub to function. Furthermore, it requires the head unit to have an available USB OTG port and a signaling path to control the hub upstream/downstream port configuration.
The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.